1. Field
This disclosure is concerned generally with the inactivation of retroviruses in immune serum globulin (ISG) and specifically with the inactivation of such retroviruses as the LAV strain of an AIDS virus in ISG intended for intravenous (IV) administration.
2. Prior Art
Therapeutic and prophylactic ISG preparations are well known and have been available for many years. ISG is presently obtained in commercial quantities using variations of a blood plasma fractionation technique developed by Cohn et al in the 1940's. Although ISG has been administered intramuscularly (IM) and more recently intravenously (IV), the latter route of administration provides numerous advantages and has gained acceptance as the preferred route of administration.
Initial attempts to render an ISG safe and effective for IV administration (IVIG) focused on eliminating its anticomplement activity. In one approach, for example, this involved chemically modifying the ISG (see U.S. 3,903,262 to Pappenhagen et al). More recently, the ISG has been made suitable for IV administration through careful pH and ionic strength control (see U.S. Pat. No. 4,396,608 and U.S. Pat. No. 4,499,073 both to Tenold). It is also known that IVIG preparations can be stabilized with carbohydrates such as maltose (see U.S. Pat. No. 4,186,192 to Fernandes et al). ISG preparations can be further purified using a variety of techniques (see, for example, U.S. Pat. No. 4,272,521 to Zuffi). Various ISG preparations having a relatively high titer to a given antigen are also well known (e.g. tetanus, hepatitis, Rho factor, etc.)
Although ISG products (both IMIG and IVIG) have been considered generally safe, there has been a growing need to assure patients that ISG products do not transmit active viruses such as those associated with hepatitis or, more recently, retroviruses such as that associated with Acquired Immune Deficiency Syndrome (AIDS). The present disclosure is based on work done to address such needs.
Antibodies to a retrovirus associated with the AIDS have been detected in human hepatitis B immunoglobulin (HBIG) (see Tedder, R. S. et al, Safety of immunoglobulin preparation containing anti-HTLV-III, Lancet 1985;1:815) as well as in other commercial lots of immunoglobulins (see Gocke, D. J. et al, HTLV-III antibody in commercial immunoglobulin, Lancet 1986;1:37-8). This observation raised the possibility that immunoglobulin products transmit infectious virus. This concern was heightened by recent reports of non A, non B (NANB) hepatitis in immunodeficient patients who had received infusions of intravenous immunoglobulins prepared from Cohn fraction II (see Webster, A.D.B. et al, Non-A, non-B hepatitis after intravenous gammaglobulin, Lancet 1986;i:322, and Ochs, H. D. et al, Non-A, non-B hepatitis after intravenous gammaglobulin, Lancet 1986;1:322-23).
Based on the above findings, we decided to determine the ability of retroviruses to withstand the various procedures employed in immunoglobulin preparations as well as other procedures. For these experiments, two prototype retroviruses were used: the mouse xenotropic type C retrovirus and the LAV strain of the AIDS retrovirus. Surprisingly, we found that the model retroviruses could be inactivated in ISG prepared by a known fractionation processing technique if that technique is followed by storage at controlled conditions of pH, temperature and time. Details of our method are described below.